but it looks confusing, since taking cylindrical-2 co-orditate system suggests R and Theta as coordinates, but not R and Z. May be its possible to redefine somewhere to R-Z instead of R-Theta? Thanks a lot for any suggestion.

There is no 2D mesh posibility in Star. The only way to run "semi-2D" cases is to make a 3D mesh with onlz one cell layer in the third direction.

The easiest way to make the mesh in any coordinate system is to use StarGUIde. Go to create mesh -> 3D, select the proper csys (number 2 in your case) and give start and end coorinate for r, phi and z. For the number of cells in r, phi and z you should give 1 for the third dimension.

If this in csys 2 then you don't need to solve for V (tangential), but should solve for U and W i.e. radial and axial. You only need cyclic boundary conditions if you have swirl, then you would need to solve for V also, as you have a 3-D problem

A model with R-Z coordinates was created and cyclic boundaries on the two faces of the model was created. But while checking the boundaries it displays an error with number 27 Cyclic boundaries are not matched.

I would like to know the reason for this error and alternative to avoid this error,